Catalysts are usually used in methods for producing hydroxyalkyl(meth)acrylate by a reaction of (meth)acrylic acid and alkylene oxide. General recognition is that homogeneous catalysts such as chromium compounds, iron compounds, and the like are preferred as the above-described catalysts. In recent years, while consideration for environment, health, and the like requires severer regulations for various wastewater, waste gas emission, and the like, there arise a strong concern for problems in potential harmfulness of disposal of catalysts, and thus desired is decrease, as much as possible, of amounts of the catalysts used in producing processes.
On the other hand, the above-described methods for producing hydroxyalkyl(meth)acrylate easily form, as by-products of impurities, dialkylene glycol mono(meth)acrylates (hereinafter, may be referred to as “biadduct”) as biadducts of alkylene oxide, leading to decrease in yield of targeted products. Therefore, all possible suppression of formation of the by-products has conventionally be en desired. In the producing method of this hydroxyalkyl(meth)acrylate, since independent introduction of alkylene oxide is accompanied by possible risk, (meth)acrylic acid is beforehand introduced. For example, Japanese Patent Application Laid-Open No. 2004-10602 proposes a process of suppressing by-production of the biadduct, wherein a higher concentration of catalysts to an amount of (meth)acrylic acid is selected in a reaction liquid at the time of reaction commencement with introduction of the alkylene oxide.